Category: Blog Posts (Page 12 of 15)
Jonathan Rooney (Fabrication Assistant at Bray) created this puppet for the Department of Drama and Dance’s winter show – The King Stag.
At Bray, we use a slotted spoil board with our CNC Router. This enables us to attach clamps to a t-slotted table below:
One of the legs in the foam jig
In the past, we have used the Rockler Hold Down Clamps to secure material. However, this clamp can damage our router bits due to collisions with the clamps:
We 3D printed clamps to mitigate this issue. The PLA and ABS plastic clamps prevented damage to the bits from collision:
However,the plastic clamps cracked under the clamping forces:
The clamps were then printed with a combination of nylon and carbon fiber on a Markforged Mark Two 3D Printer:
These clamps were much stronger and able to flex without cracking. The clamps were tested on the mill to simulate a bit collision. The milled carbon fiber broke into fairly large chips. There was a concern that the carbon fiber and nylon material might melt onto the bit. However, the bit came out clean. Check out the video clip below:
Testing carbon fiber clamp on mill
Mechanical Engineering students designed an injection molding machine for a senior design course.
A 6’7″ friend of mine came to me asking if I could build a more elegant solution to his makeshift cardboard box computer stand
So I decided to make a stand for him using the DI-wire. I started with brainstorming ideas and settled on a final geometric triangular design. The sides would be made using the DI-Wire and the top would be made out of a piece of acrylic
I used the manual function on the DI-Wire to bend three pieces of steel wire into the different triangular shapes (the green, red, and blue shapes) that made up the geometric design. I then used a technique called braising which is like welding but for thinner metals. I braised the top wires together to form the design and then braised six points of the design (the ones circled in red) for structural support.
Next, I laser cut and bent acrylic over different parts of the design to give it a stained glass look. To bend the acrylic I cut tabs out on the laser cutter and I used a heat gun to heat the tabs until they were flexible enough to bend. I would then bend it over the metal wire wearing gloves and would hold it in place until it cooled and solidified. To further the stained glass look I made a geometric design inspired by mountains and used puffy paint to paint it onto the acrylic. I then plan on filling in the different sections of the puffy painted design with glass stain so it has the appearance of stained glass.
I was still debating how to attach the sides to the acrylic when my co-workers and I went on a field trip to Artisan’s Asylum. There I found inspiration for how to do just that. One of the artists who worked there had attached metal wires to a log by braising washers to the ends of the rods. This is what I then did to attach the sides of the stands to the top of the acrylic.
I laser cut holes into the acrylic and added threaded inserts using a soldering iron to heat up the insert and push it into the acrylic. This allowed me to screw the washers at the ends of the wires right into the acrylic top. I also laser cut more tabs into the acrylic and used the same method of acrylic bending that I used before to bend the tabs over the wires for extra support.
Finally I added a cross support across the back of the stand to give it more support and prevent it from wobbling. I braised the middle of the cross support to secure it in place. All I have to do now is paint the sides and the stand will be complete.
After a long summer of brainstorming, ideating, prototyping, and revising, the picture frame is finally ready for deployment in the shop. Last week’s “wrap-up” frame design prompted the comment that most people print 4×6 pictures, not 5×7, leading to some quick dimension changes and the construction of a final prototype. This new frame holds 4×6 pictures snugly (a practical, appealing function), takes about 2 hours to make under ideal circumstances (commensurate with the wall hook), and lowers the cost by almost a dollar, down to $5.02 per frame (coverable by a small lab fee, as discussed in last week’s post).
As of now, the picture frame is officially a training option for those looking to use the yellow zone tools. All of this project’s goals were met successfully: the frame adds interest to the project, covers every tool in the yellow zone and incorporates some from outside, and is easily manufacturable by those new to the shop. With luck, these frames will soon grace shelves all across engineering dorm rooms at Tufts.
After spending the majority of the summer brainstorming, sketching, designing, modeling, and practicing the techniques required to build a table, we were able to assemble the final coffee table this week.
The first step in assembling the table was to mill the legs on the ShopBot. The way the legs were designed allowed me to run the same CNC program one time on each leg. To ensure that the program started and ended in the same place every time, I cut out a foam jig to clamp down on the ShopBot bed and then placed the leg in the jig.
One of the legs in the foam jig
Once the leg was done being milled, I was able to remove it without moving the jig, place a new leg in, and run the same program without having to re-zero any of the axes. I used a 1/4″ end mill bit to get a flat cut for the wrap to rest on.
Once Ben had completed the finger joints, we were able to put the table wrap together and fit the legs in. Unfortunately, some of the legs stuck out too far from under the wrap. The amount of material we needed to take away was too much for sandpaper or a hand planer, but too little for a table saw. Thankfully, there is a planing bit for the ShopBot (seen below).
Unlike the end mill and ball nose mills, the planing bit cannot plunge
Having only used that bit once with HDPE, I was reluctant, but it was looking like our best option. I placed my legs back into the foam jig I used earlier, switched out the 1/4″ end mill bit for the planing bit, and used a .1″ pocket cut on two faces of each leg.
One of the table legs being planed
Once the wrap fit on the legs, I moved on to milling the model of Tufts. The pieces of plywood I was using were 22-1/2″ x 17-3/16″ x 1-1/2″, which is just about the size of the ShopBot bed (which is 24″ x 18″). This left very little room to put any clamps on, let alone enough clamps to make sure the piece wasn’t going to move while it was being milled. The few clamps I could get on were difficult to hold down as the knobs were too wide in diameter and kept hitting the sides of the stock piece. I decided to design a corner clamp (seen below) that would keep my piece square, straight in the X and Y directions, and have enough room to use the knobs without getting in the way of the material or the bit.
Corner clamp
I 3D-printed the clamps so that in case they did get in the way of the bit, they wouldn’t damage the bit and could easily be re-printed. I did one final, to-scale model of the Tufts map in foam with the 1/” end mill bit before I used the plywood. The foam model turned out just as expected.
The practice foam being milled
I left the clamps in the same position, and just switched out the foam for the plywood, and ran the same program.
The plywood being milled for the final model
I repeated that process with the rest of the map sections to produce the base layer of the map.
Coffee table with the base layer of the model in place
The two top layers are currently being milled and will be added to the table shortly. The rest of the table has been stained and is about ready to be moved to it’s final destination in the Design Lab!
Purpose: One of the goals for this summer at Bray was to find a way to help organize the material in the machine shop. We noticed the rack near the laser cutter held three disorderly piles of acrylic which were difficult to sift through to find the right piece. To fix this, we decided to create rack dividers that would show off some the of what can be done in the shop.
Design: Considering the rack was our environment, we came up with a divider that could easily clip into the rungs on the rack. Wanting at least three points of connection as well as geometric sturdiness, we decided to make steel framed triangular dividers. The process for making these involved four steps: cutting and brazing the wires, laser cutting and etching the acrylic, heating bending the acrylic into the steel frame, and joining the divider into the rack itself.
Major Resources Used
Step 1: Cutting & Brazing
The frame consisted of three wires, 14″, 24″, and a 25.5″. After cutting the wire ends are sharp and must be deburred with a file. After bending 1 inch of the 24” over to make a loop, the last step before brazing is to sandpaper off the steel coating at the binding joints.
Brazing Components
Brazing is the process of binding two pieces metal with brass filler by torch. The three steel pieces are brazed to be connected as shown below. Proper brazing training is required to assemble.
Step 2: Laser Cutting and Etching
An acrylic plate is laser cut to internally fit the steel frame. We etched an aesthetic Bray logo on the side as well. The tabs will wrap around the steel frame by a process known as heat bending.
Step 3: Acrylic Heat Bending
Each of the six tabs are heated with a heat gun and bent around the wire, cooling and settling in a securing and binding form to the steel frame. This process has been used in at least one other summer project and shows promise as a useful skill for creating sturdy and functional plates.
Heat Gun Applied to Acrylic Tabs
Step 4: Installing the Dividers
The dividers should have extensions past all three endpoints. The first one is the hook made earlier. Installing the dividers starts with appropriately placing this hook and the rest of the body into the desired location on the rack.
Initial Top Hook
Next, the bottom two extensions need to be bent to secure in the divider. This was done by a set of slip joint pliers, groove joint pliers, and long nose locking pliers. The coil (below) around the front was difficult to obtain since there were very bad angles for most of the turns and the steel is tougher then the rack material itself.
Front Coil
Final Result
Aesthetically Pleasing and Efficient Use of Space
Holds Significant Quantity of Acrylic. Organized by Sheet Thickness and Size
Further: These racks were successful in design and implementation. Since the dividers are close, they can hold more acrylic by lowering the horizontal force while leaning. Different acrylic inventory in the future can also be accounted for by moving which type of material is where. There are also plans for creating modular labels are on the way and which will further ease the trouble of finding just the right sheet to make your laser cut.
More of these can be made on the other shelf (or another rack!) to help store foam and wood material in the shop. The design of these dividers were made in such a way that they could be modified for other racks or spaces to help organize. If another iteration of these dividers are made, we suggest changing the reliefs to be more rounded in order to distribute pressure along the tabs’ bases. Also, if any of these dividers break, it should be easy to clip that divider out and install a new one by the same method outlined above.
After a third prototype and some experiments with acrylic forming, the picture frame is, I believe, nearing completion. This prototype, shown below, goes for more of a “polished-industrial” feel that hides a larger purpose: the cap nuts securing the vertical frames to the acrylic plate allow for zero-tools insertion of a picture, something that was not possible in the previous two designs and could preclude many students from using their frames.
Compared to the wall hook, this frame has several key advantages that I believe make it an ideal shop training project, either as a supplement to the hook or as a complete replacement.
- Scope: The wall hook required only three yellow zone tools: the horizontal bandsaw, the drill press, and the jump shears. Students used the vertical bandsaw for a single cut, but with the caveat that they weren’t really supposed to use it for what they were doing—an odd thing to say during shop training. The picture frame, by contrast, requires five yellow zone tools, incorporating the hand drill and laser cutter into the original three. Additionally, the plate stock, while cut entirely on the jump shears for the prototype, could be cut properly on the vertical bandsaw with no caveats, thus making for six tools used properly.
- Variable tool usage: Of the wall hook’s 31 required power tool operations, a whopping 26 of them (84%) took place on one of the shop’s three drill presses. This high percentage of drilling and countersinking operations created major bottlenecks when large numbers of students were trained at once. The picture frame spreads out the tool usage much better, with only 18 of its 32 operations (56%) taking place on the drill press. The plate work on the supports could be split evenly between the jump shears and vertical band saw, reducing bottlenecks even further. The only real potential for a major bottleneck is at the laser cutter, but I believe efficient management of it so that multiple students are trained and cutting their single part at the same time could make its use manageable.
- Variable parts: The wall hook’s five pieces were all very similar (or, in two cases, exactly the same), each requiring almost the same order of operations. By contrast, each of the picture frame’s three unique components (two components are mirror images) requires a completely different set of skills from the others: the acrylic backing plate is laser-cut; the bar stock frames are cut on the horizontal bandsaw and drilled on the drill press; and the plate supports are cut on the jump shears or vertical bandsaw, hand-drilled, and countersunk on the drill press. And because the drill presses are split, two for drilling and one for countersinking, there is no tool usage overlap between parts as there was with the wall hook. If there is a line at the drill press, those not in line can work on a part that does not require the drill press, something that was not possible with the wall hook.
- Less tapping: The picture frame has half as many tapped holes as the wall hook, giving students the opportunity to get a feel for the process but giving them fewer chances to break a tap.
- Interest level: The wall hook perhaps received the most grief because of its lack of utility in a college dorm. Because the dorms forbid screwing into walls, most students could not make use of their hooks, leading to a lack of interest from those students who were not interested in the act of making something. The picture frame, requiring no mounting, presents a desirable end goal for those more results-driven than process-driven.
All of these advantages together, I believe, outweigh the one major disadvantage the picture frame presents: cost. Considering only the cost of materials in the finished product—that is, not accounting for students breaking taps, remaking parts, etc.—the frame costs $5.96, compared with the wall hook’s mere $0.74 price tag. I would argue, however, that the expanded scope and heightened interest level present a compelling case for adopting the picture frame and adding a small lab fee to the course. I believe most Tufts students would be fine paying a small price for a more useful end product; furthermore, it is almost expected in other disciplines here that courses with lab components are going to have a lab fee. For biology or chemistry, these fees can reach into the hundreds of dollars; by contrast, a $5 or $10 fee would seem insignificant, especially if it is clear that it pays for a concrete end product.
Several prospective students on a tour were asked about shop training projects, and while they thought the wall hook was decent and liked the pen holder more, they all agreed that the picture frame held the most appeal for them. I think many students would feel the same, given the choice between something they cannot really use and something that they may already want. And the more concrete advantages only add benefits.
Map of Bray
First Floor
Second Floor
